The reasons for the floc floating in the clarifier are multi-faceted. It will directly affect the effluent quality, so it should be taken seriously. The reasons for the large amount of floc floating in the clarifier are as follows.

(1)The rotational speed of the agitator in the clarification tank is too high, which breaks up the flocs. It is even more difficult for the broken flocs to coagulate again, causing the strength of the sludge to decrease and the flocs to float up. When encountering such a situation, the linear velocity at the outer edge of the mixer impeller should be well controlled and must not exceed the design specification. At the same time, the dosage of coagulant should be appropriately increased to re-form the suspended sludge layer.

(2)The reflux gap of the clarifier is clogged, preventing the activated sludge from flowing back and causing flocs to float up along the tank wall. At this point, the reflux joint should be opened to flush the pipeline, clear the blockage, appropriately drain the sewage, and increase the reflux flow and water volume of the mixer4~5By doubling, the upward floating phenomenon can be avoided.

(3)Failure to discharge pollutants in a timely and regular manner, or significant fluctuations in the height of the sludge layer, or an excessively high sludge layer, can cause flocs to float up. At this point, it is necessary to promptly carry out sludge discharge and adjust or control the height of the sludge layer properly.

(4)The dosage of coagulant is small, making it difficult to form flocs, resulting in poor coagulation effect and failure to separate and settle suspended solids. Or if the dosage of coagulant is too large, a counter-ion phenomenon occurs, making it difficult to coagulate and also causing flocs to float up.

(5)The sudden change in water temperature causes disturbances in the water flow, and the sludge layer floats up. At this point, the stirring speed can be appropriately reduced and the dosage of coagulant can be increased to adjust the water output and stabilize the water flow. If possible, activated mud or slime can be added appropriately.

(6)If it is a clarifier with lime slurry added, if the dosage is too large, calcium carbonate colloid will be formed, causing the flocs to be large in volume but low in density, and they are prone to float up. If the dosage is too small, the calcium carbonate precipitate formed will be small, the volume of flocs will be small, and the strength of the sludge layer in the reaction zone will decrease and float up. At this time, the speed of the agitator should be appropriately adjusted, the alkalinity should be stably controlled, and the dosage of coagulant should be appropriately increased.